Alkylate having improved sulfonating characteristics



Sept. 9, 1958 ALKYLATE HAVING IMPROVED SULFONATING CHARACTERISTICS Filed001:. 20. 1954 W. H. SHIFFLER DJ E 5 a I 5 2 HF 0 w T n t O. (D

ALKYLATION w 2 L :11 HF I v 2 w LL] SETTLING F Ll. I

HF HYDROCARBON REGENERATION V [I LIGHT l DIST! LLATION ALKYLATE BOTTOMSy w 2 HF ALKYLATE K n Z BENZENE g 1 TREATING ZONE 2 Q '2 l :1 SETTLER VO HF HYDROCARBON HF- BENZENE 5 '2 v I ..J

a: 9 O K HF STRIPPER Y 1 BENZENE E BENZENE STRIPPER STEAM TREATEDALKYLATE SETTLER 0 1 INVENTOR W/LL/AM SH/FFLER .sold for use in theproduction of sulfonates.

Unite rates ALlKYLATE HAVING IMPROVED SULFONATING CHARACTERISTICSApplication October 20, 1954, Serial No. 463,390 4 Claims. (Cl. 260-671)This invention relates to a process for producing alkyl benzenes havingimproved sulfonating characteristics. More particularly, it relates to amethod for treating alkyl benzenes prepared by alkylating benzene withlower olefin polymers to improve the sultonating properties of the alkylbenzenes.

The great bulk of the synthetic sulfonate detergents currently producedis prepared by sulfonating alkyl benzenes of the character described inU. S. Patent No. 2,477,382. Alkyl benzenes of this character areprepared by polynierizing lower olefins, in particular propylene andbutenes, or mixtures of propylene and butenes, to produce polymerfractions containing 8 to 18 carbon atoms per polymer molecule. Benzeneis then alkylated with the polymers and the alkylation reaction mixtureis fractionally distilled to separate a heart cut alkylate materialcharacterized by having a number of carbon atoms in the alkyl sidechains corresponding to the number of carbon atoms in the polymermolecules employed in the alkylation reaction. In the distillation,lower alkyl benzenes containing 4 to 7 carbon atoms in the alkyl sidechains, and higher alkyl benzenes and dialkyl benzenes containing alarger aggregate number of carbon atoms in the alkyl side chains thanwere contained in the polymer employed in the alkylation, both of whichare produced by side reactions such as disproportionation,polymerization and alkylation which occur during the main alkylationreaction, are rejected from the whole alkylation reaction productmixture.

The alkylates produced in the above-described manner have proven highlysatisfactory materials for use in the production of synthetic detergentsby sulfonation, neutralization and compounding with builders, foamadjuvants, and the like. These materials are used in the production ofmillions of pounds of synthetic sulfonate detergents each year.

As the synthetic sulfonate detergent market has developed, rigorousproperty requirements have been imposed on the alkyl benzenes which areproduced and The alkyl benzenes must yield a sulfonate which isessentially pure white in color, which is free of cracked orkerosene-like odor, and which is extremely low in residual sulfonatedoil. The sulfonates produced by sulfonating .alkyl benzenes obtained byalkylating benzene with lower olefin polymers commonly exhibitundesirable color and odor characteristics.

It is an ob'ect of this invention to provide a method for treating alkylbenzenes produced by alkylating benzene with lower olefin polymers toeifect a substantial improvement in the sulfonating characteristics ofthese alkyl benzenes and, in particular, to produce a treated alkylbenzene which yields a sulfonate product of superior color.

It has now been found that the sulfonating characatent 2 teristics ofalkyl benzenes prepared by alkylating benzene with lower olefin polymerfractions containing from 8 to 18 carbon atoms per molecule can be verymarkedly improved by intimately mixing the alkylate with substantiallyanhydrous hydrofluoric acid and benzene, settling the resultant mixtureto separate a predominantly hydrocarbon layer and an acid layer, andfractionally distilling the hydrocarbon layer to separate hydrofluoricacid and benzene from it.

Color measurements of synthetic sulfonates are commonly made by theTristimulus'Method of Color Determination, described in Handbook ofColorimetry, A. T. Hardy, 1936, Technology Press, M. I. T., Cambridge,Massachusetts. The color data reported hereinafter were determined bythis method.

EXAMPLE 1 An allryl benzene prepared by alkylating benzene, pursuant toU. S. Patent No. 2,477,382, with a propylene polymer prepared bypolymerizing a predominantly propylene feed and having an A. P. I.gravity of 49.7 and ASTM-D-86 distillation inspections as follows:

was treated with hydrofluoric acid and benzene pursuant to theinvention. The properties of the alkyl benzene subjected to thetreatment are shown in Table I below. The treatment was carried'out byvigorously mixing the alkyl benzene with substantially anhydroushydrofluoric acid and benzene at F. for 10 minutes. The resultantmixture was then stirred for 15 minutes to separate an upper hydrocarbonlayer and a lower acid layer. The hydrocarbon layer was washed to removeresidual acid, distilled under a vacuum to remove the major part of thebenzene, and steam stripped to remove the final traces of benzene. Thedata in Table I sets out the properties of the treated and untreatedalkylates. The mol ratio of. alkylate to benzene to HF employed in theproduction of the treated alkane described in Table I was 1:1:10.

Table I alkylate HF Treated Untreated Saybolt Color Color, PercentSaturation 1 5 S03 Sulfonate Slurry Color, Percent Saturation Viscosityat F., SSU rnillne Point, "I?

Gravity, API Dialkylbenzenes, Percent Distsiltlation, D-447:

EXAMPLE 2 The untreated alkylate described in Table I was subjected tofurther treatments in which the proportions of m mos V ,3 hydrofluoricacid and benzene were varied. The results of these treatments are shownin Table II.

1 The treated alkylate showed an increase in dialkyl benzene cont nt of4.3 volume percent.

EXAMPLE 3 A higher boiling alkylate prepared by alkylating benzcne withpropylene pentamer and separating a heart out pentamer alkylate fractionwas treated with benzene and hydrofluoric acid as in Example 1. Theuntreated alkylate on an ASTM-D-447 distillation had:

F. Initial boiling point 559 5% point 578 50% point 594 95% point 614The untreated alkylate itself had a Saybolt color of +12, while thetreated alkylate had a Saybolt color of +25. The sulfonates produced byidentical sulfonation treatments from the treated and untreatedalkylates had tristimulus colors of 17% saturation and 22% saturation,respectively. The sulfonates in Examples 1 and 2 were prepared bysulfonating the alkylate by passing a stream of air and S containing 5to S0 through the alkylate at C. until sulfonation was complete. In eachcolor comparison made in Examples 1 and 2, the conditions of sulfonationwere rigorously controlled and were identical for the sulfonation ofboth the treated and untreated samples. The SO -air sulfonationtechnique is growing in commercial importance in that it produces aneutral sulfonate having a low sodium sulfate content. This method ofsulfonation causes substantially greater formation of color bodiesduring the sulfonation of any given alkylate than does the older methodof sulfonation in which fuming sulfuric acid is employed as thesulfonating agent. The sulfonation of the two samples compared inExample 3 was carried out with 20% fuming sulfuric acid and thesulfonation conditions were identical.

From the data tabulated in the above examples, it is clear that verymarked improvements in color of the sulfonate product are obtained whenthe alkylate is treated with hydrofluoric acid and benzene prior tosulfonation.

The presence of benzene during the treatment is required to suppress theformation of dialkyl benzenes during the treatment. This is clear fromthe data in Table II. Dialkyl benzenes are highly undesirable in thealkylate subjected to sulfonation, since their presence increases theamount of residual unsulfonated oil in the sulfonate product and impartsa marked odor characteristic of cracked petroleum products to thefreshly prepared sulfonate. The production of dialkyl benzenes duringthe treatment of the alkylate must, therefore, be suppressed.

A number of treatments of alkyl benzenes prepared by alkylating benzenewith propylene polymers, butene polymers and mixed propylene-butenepolymers was carried out using varying proportions of benzene andhydrofluoric acid. It was found that in order to effect a significantimprovement in the sulfonating characteristics of the alkyl benzene, theratio of hydrofluoric acid to alkylate in the treatment must exceed 0.5mol of HF per mol of alkylate and that the ratio of benzene to alkylatein the treatment must exceed 0.25 mol per mol of alkylate. The employment of extremely high mol ratios of HF to alkylate and benzene toalkylate was found to produce treated alkylates having excellentsulfonating characteristics. It was observed, however, that littleincremental improvement is obtained by employing hydrofluoric acid toalkylate mol ratios above 2021, or by employing benzene to alkylateratios above about 10:1.

The treatment of the alkylate with benzene and hydrofluoric acid isordinarily conducted at atmospheric temperature; temperatures oftreatment may be higher or lower than atmospheric, for example,temperatures in the range 30 to 200 F. are fully operative.

A further significant characteristic of the treating method lies in thefact that the removal of hydrofluoric acid and benzene from the treatedalkylate when the treatment is complete must be accomplished attemperatures below 400 F., and preferably below 350 F. if the fullbenefit of the treatment is to be realized in the final product.Accordingly, it is preferred to settle the mixture of benzene,hydrofluoric acid and alkylate at the end of the treatment to separatean upper hydrocarbon layer and a lower acid layer, and then to removethe hydrocarbon layer and distill residual hydrofluoric acid from itwhile maintaining the maximum temperature in the still pot below 350 F.,and desirably at about 300 F., and then to remove residual benzene bysteam distillation at temperatures below 300 F. If it is attempted tosubject the mixture of treated alkylate, benzene and HP to conventionaldistillation at atmospheric pressure to remove hydrofluoric acid andbenzene, still bottom temperatures of the order of 450 F. or higher mustbe employed in order to complete the removal of these two materials.Under such conditions it appears that a thermal degradation of thetreated alkylate occurs, and it is found that upon sulfonation treatedalkylate distilled in this manner shows much less color improvement thanis obtained if the distillation temperatures are held below 350 F.

The appended drawing is a diagrammatic illustration of a process flowsuitable for the practice of one embodiment of the invention in whichhydrofluoric acid is employed as both the alkylation catalyst and thetreating agent. Hydrofluoric acid, polymer and benzene are charged to analkylation zone in which the alkylation is conducted pursuant to U. S.Patent No. 2,477,382. The alkylation reaction product is settled toseparate a lower acid phase, a portion of which is recycled to thealkylation zone, and a portion of which is directed to a regenerationzone. In the regeneration zone the spent or partly spent hydrofluoricacid is fractionally distilled to remove essentially pure anhydroushydrofluoric acid overhead and to separate a bottoms fraction comprisingtarry materials contained in the spent acid and water in the form of theconstant boiling HF Water azeotrope. The hydrocarbon layer isfractionally distilled to separate a fraction comprising HF and benzene,which is returned to the alkylation' zone, a light alkylate fractioncharacterized by a substantial content of alkyl benzenes containing from4 to 7 carbon atoms in the alkyl group, a heart out alkylate having anumber of carbon atoms in the alkyl side chain corresponding to thenumber of carbon atoms contained in the polymer molecules charged to thealkylation zone, and a heavier bottoms fraction. The heart cut alkylate,benzene and HF are passed into a treating zone where these threematerials are vigorously mixed for a period of from 1 second to minutes.Very short contact times of the order of one second give satisfactoryresults when, for example, the alkylate, benzene and hydrofluoric acidare passed through an efficient line mixer and then directly into asettler. The mixture from the treating zone is passed into a settler toseparate an upper hydrocarbon phase and a lower acid phase. A portion ofthe acid phase is recycled to the treating zone and a portion of it isrecycled to the HF regeneration zone and to the alkylation zone,desirably via the settling vessel following the alkylation zone in theprocess flow. The hydrocarbon layer is fractionally distilled at amaximum still bottom temperature usually in the range from 275 F. to 325F. to remove substantially all of the HF overhead. This overhead HF isreturned to the treating zone. After the stripping of the HF from thehydrocarbon layer is complete, the residual hydrocarbon material ispassed into a benzene stripper where benzene is separated from thetreated alkylate by steam distillation at a temperature usually in therange from 225 F. to 300 F. The benzene stripped from the treatedalkylate is passed through a drier, distilled to remove lower alkylbenzenes and returned to the alkylation zone. This benzene stream may,if desired, be returned directly to the alkylation zone or a portion ofit may be returned directly to the treating zone. This benzene is foundto have an appreciable content of lower alkyl benzenes, however, and thebulk of it is, therefore, desirably distilled before return to thealkylation zone or to the treating zone. After the benzene stripping iscomplete, the treated alkylate is settled to separate water andwithdrawn for sulfonation.

In pilot plant operation of the treating process above described, it hasbeen observed that the desired improve ment in the sulfonatingcharacteristics of the alkylate can be obtained with very littleaccompanying stock loss. For example, in pilot scale treating employingten mols of hydrofluoric acid and one mol of benzene per mol ofalkylate, it was found that the volume of treated alkylate product was99.3%.

I claim:

1. A process for improving the sulfonating characteristics of alkylatesprepared by alkylating benzene with olefin polymer fractions containing8 to 18 carbon atoms per polymer molecule, which comprises fractionallydistilling the crude alkylate to separate a heart cut alkylateconsisting essentially of monoalkyl benzenes having alkyl side chainscontaining a number of carbon atoms corresponding to the number ofcarbon atoms in the polymer charged to the alkylation zone, intimatelymixing said heart out alkylate with benzene and substantially anhydroushydrofluoric acid, the quantities of hydrofluoric acid and benzene beingsuch that in the resulting mixture the mol ratio of hydrofluoric acid toheart cut alkylate is in excess of 05:1 and the mol ratio of benzene toheart cut alkylate is in excess of 0.25:1, settling the resultantmixture to separate a predominantly hydrocarbon layer and an acid layer,and stripping hydrofluoric acid and benzene from the hydrocarbon layerbelow about 400 F.

2. A process for improving the sulfonating characteristics of alkylatesprepared by alkylating benzene with olefin polymer fractions containing8 to 18 carbon atoms per molecule, which comprises fractionallydistilling the crude alkylate to separate a fraction having an initialboiling point above about 500 F., and consisting essentially ofmonoalkyl benzenes intimately mixing said fraction with substantiallyanhydrous hydrofluoric acid and benzene, the quantities of hydrofluoricacid and benzene being such that in the resulting mixture the mol ratioof hydrofluoric acid to said fraction is in excess of 0.5:1

and the mol ratio of benzene to said fraction is in ex cess of 0.25 :1,settling the resultant mixture to separate a predominantly hydrocarbonlayer and an acid layer and fractionally distilling the hydrocarbonlayer to separate hydrofluoric acid and benzene while maintaining themaximum temperature during said distillation below 400 F.

3. A process for improving the sulfonating characteristics of alkylatesprepared by alkylating benzene with olefin polymer fractions containing8 to 18 carbon atoms per polymer molecule and distilling the resultingcrude alkylate to separate a desired alkylate fraction consistingessentially of monoalkyl benzenes, which comprises intimately mixing thedistilled alkylate with 0.5 to 20 mols of substantially anhydrous HF andwith 0.25 to 10 mols of benzene per mol of alkylate, settling theresultant mixture to separate a predominantly hydrocarbon layer and anacid layer, subjecting the hydrocarbon layer to fractional distillationat a maximum distillation temperature below about 350 F. to separatehydrofluoric acid from the hydrocarbon layer, and then subjecting theresultant substantially acid-free hydrocarbon layer to steamdistillation at a temperature below about 300 F. to separate benzene.

4. A process for producing alkyl benzenes having im-' proved sulfonatingcharacteristics, which comprises alkylating benzene with lower olefinpolymer containing 8 to 18 carbon atoms in the polymer molecule in thepresence of hydrofluoric acid as the alkylation catalyst, settling thealkylation reaction mixture to separate a hydrocarbon phase and an acidphase, returning a portion of the acid phase to the alkylation zone andintroducing a portion of the acid phase into a regeneration zone andthere regenerating the acid, fractionally distilling the hydrocarbonphase to separate a heart cut alkylate consisting essentially ofmonoalkyl benzenes having alkyl side chains containing a number ofcarbon atoms corresponding to the number of carbon atoms in the polymercharged to the alkylation zone, intimately mixing said heart cut withregenerated hydrofluoric acid and benzene in a treating zone, settlingthe mixture to separate a hydrocarbon phase and an acid phase, returninga portion of the acid phase to the treating zone and a portion to thealkylation zone, fractionally distilling the hydrocarbon phase to efiectsubstantially complete separation of hydrofluoric acid and benzene fromthe heart out alkylate while maintaining the maximum distillationtemperature below 400 F., returning the separated hydrofluoric acid tothe treating zone and returning the separated benzene to the alkylationzone and stripping residual benzene from the hydrofluoric acid-freehydrocarbon phase below a temperature of about 300 F.

References Cited in the file of this patent UNITED STATES PATENTS2,378,762 Frey June 19, 1945 2,477,383 Lewis July 26, 1949 2,534,072Schulze Dec. 12, 1950 2,626,967 Darragh et al. Jan. 27, 1953v

1. A PROCESS FOR IMPROVING THE SULFONATING CHARACTERSTICS OF ALKYLATESPREPARED BY ALKYLATING BENZENE WITH OLEFIN POLYMER FRACTIONS CONTAINING8 TO 18 CARBON ATOMS PER POLYMER MOLECULE, WHICH COMPRISES FRACTIONALLYDISTILLING THE CRUDE ALKYLATE TO SEPARATE A HEART CUT ALKYLATECONSISTING ESSENTIALLY OF MONOALKYL BENZENES HAVING ALKYL SIDE CHAINSCONTAINING A NUMBER OF CARBON ATOMS CORRESPONDING TO THE NUMBER OFCARBON ATOMS IN THE POLYMER CHARGED TO THE ALKYLATION ZONE, INITIMATELYMIXING SAID HEART CUT ALKYLATE WITH BENZENE AND SUBSTANTIALLY ANHYDROUSHYDRODLUORIC ACID, THE QUANTITIES OF HYDROFLUORIC ACID AND BENZENE BEINGSUCH THAT IN THE RESULTING MIXTURE OF MOL RATIO OF HYDROFLUORIC ACID TOHEART CUT ALKYLATE IS IN EXCESS OF 0.5:1 AND THE MOL RATIO OF BENZENE TOHEART CUT ALKYLATE IS IN EXCESS OF 0.25:1, SETTLING THE RESULTANTMIXTURE TO SEPERATE A PREDOMINATELY HYDROCARBON LAYER AND AN ACID LAYER,AND STRIPPING HYDROFLUORIC ACID AND BENZENE FROM THE HYDROCARBON LAYERBELOW ABOUT 400*F.